The significance of the double cask matured means that part of the whiskey matures on traditional drums, the other to ex-sherry butts. The traditional drums, also refill casks' called, contribute to the development of the subtle flavors in the whiskey. Sherry butts contribute to the development of rich aromas and give the whiskey a ruby golden color. After at least 12 years of traditional drums are merged with the ex-sherry butts.